The broad long term objective of this project is to obtain a fundamental understanding of the basic biophysical and physiological mechanisms of task-induced contrast in human functional Magnetic Resonance Imaging (fMRI). This understanding can be expected to provide a basis for the application of fMRI to the field of neuroscience. The present study will test the hypothesis that dynamic BOLD (blood oxygenation level dependent) fMRI contrast has vascular and metabolic components that vary over time and space, and that with sufficient a priori information, measurement of particular aspects of the BOLD signal can provide unique information about the physiological events resulting from task activation.